COLUMN LIQUID-CHROMATOGRAPHY COUPLED ONLINE WITH MASS-SPECTROMETRY USING POSTCOLUMN PHOSPHATE SUPPRESSION

The coupling of column liquid chromatography on-line with mass spectro metry using post-column phosphate suppression is described. A membrane suppressor is used to remove the non-volatile phosphate ions from the mobile phase after the chromatographic separation prior to introducti on into the mass spectrometer. Using post-column phosphate suppression by a membrane device phosphate concentrations up to 10 mM phosphate, at a mobile phase flow rate of 0.1 ml/min, could be removed for more t han 99% without any decay of the sensitivity of the MS detection. Usin g a new antidepressant tetracyclic basic compound, ORG 4428, and some structure related compounds as model compounds electron impact as well as chemical ionisation spectra of all compounds could be obtained. Th e set-up could be used for several weeks running, using a phosphate co ntaining mobile phase, without any loss of performance.